How to move objects at the nanoscale

A new study published in PNAS

To move a nanoparticle on the surface of a graphene sheet, you won’t need a “nano-arm”: by applying a temperature difference at the ends of the membrane, the nanocluster laying on it will drift from the hot region to the cold one. In addition, contrary to the laws ruling the world at the macroscale, the force acting on the particle – the so-called thermophoretic force – should not decrease as the sheet length rises, sporting a so-called ballistic behavior. In fact, simulations show that vertical thermal oscillations of the graphene membrane flow ballistically from hot to cold, providing a push to the object. Yet these vertical waves, known as flexural phonons, should not be able to impress any lateral shift to an object. Nevertheless, computer simulations show that they do push the nanocluster in the same way a surfboard is taken to shore by ocean waves. And, of course within limits, no matter how far away the wave came from. These theoretical predictions could be of great interest in the frame of manipulating materials at the nanoscale, in view of potential technological applications. The research, which was conducted by a joint SISSA-ICTP group and funded by a European ERC Advanced Research Grant, has been recently published by co-authors Emanuele Panizon, Roberto Guerra and Erio Tosatti, coordinator of the study, in Proceedings of the National Academy of Sciences (US).